The present invention generally relates to a system and method for improved collision detection between a movable component of an imaging device and an object. In particular, the present invention relates to improved collision detection using a real-time process for adaptively obtaining motion parameters of a movable component of an imaging system.
Medical diagnostic imaging systems encompass a variety of imaging modalities, such as x-ray systems, computerized tomography (CT) systems, ultrasound systems, electron beam tomography (EBT) systems, magnetic resonance (MR) systems, and the like. Medical diagnostic imaging systems generate images of an object, such as a patient, for example, through exposure to an energy source, such as x-rays, for example. The generated images may be used for many purposes in analyzing the object such as detecting internal defects, determining changes in internal structure or alignment, or tracking fluid flow within the object. Furthermore, the image may show the presence or absence of certain elements in an object. The information gained from medical diagnostic imaging has applications in many fields, including medicine and manufacturing.
Medical diagnostic imaging systems often require the motion of a subsystem in proximity to an object. For example, in acquiring fluorographic images, an x-ray source and image sensor are moved to various locations about a patient to obtain multiple views of the patient's anatomy. In another example such as acquiring CT slice data, an x-ray source and/or sensor are rotated about a patient to obtain the desired imaging. As the subsystem moves about the object to obtain the medical diagnostic data, collisions may occur with the patient or other objects in proximity to the moving subsystem.
Movement of a diagnostic imaging subsystem is typically accomplished using a servo system, that is, an electromechanical system that performs mechanical movement generally using software control along with feedback. A collision or impending collision of a moving subsystem with an object generally is monitored using one of two types of anti-collision sensors: contact sensors and proximity sensors, which typically are associated with bumpers or other targeted regions on the diagnostic imaging system. Monitoring and adjustments for collisions or impending collisions can also be accomplished using feedback and/or feed forward processes within the servo system of the diagnostic imaging system.
It is important in a diagnostic imaging system to obtain early detection of a collision between a moving subsystem and a patient, or other obstruction. The use of feedback signals can provide more universal sensing capability than the use of contact and proximity sensors because feedback signals can provide information on resistance to a directed motion anywhere along the moving subsystem. However, normal operation of a servo system can also create feedback signals that are not due to a collision but are similar to a signal that a collision would induce. Additionally, feedback and/or feed forward signals may be processed in a way that allows a diagnostic imaging system to inherently be less aggressive in powering motion against a collision, while at the same time retaining the desired aggressiveness in powering motion resulting from an input control signal.
Motion control signals associated with feedback for a moving subsystem of a diagnostic imaging device can be monitored to sense a collision. Monitoring data from motion control signals associated with feedback can be used to prevent false collision detection that can occur due to feedback signals. Furthermore, the use of feed forward can suppress a collision, thereby lowering the chance that the collision creates motion problems or damage associated with the moving subsystem of the imaging devices. Feed forward is useful for optimizing the collision detection performance of a moving subsystem in an imaging device. However, the accuracy of feed forward decreases when presumed motion parameters that are associated with the hardware of a servo system for a moving subsystem do not reflect the actual servo system hardware. In general, inaccuracies in the motion parameters associated with all aspects of the moving subsystem hardware can detract from collision detection. Furthermore, feed forward can be particularly sensitive to degradation due to errors in the presumed values of hardware motion parameters.
Thus, there is a need for systems and methods for obtaining and using enhanced hardware motion parameters for moving subsystems to improve collision detection in imaging systems.